U0014: Medium Speed CAN Communication Bus (+) High
What to do
This is one of the faults that can damage things rather than just stopping them, so read U0005 before repairs are discussed. Full battery voltage has got onto a network wire, and every computer on that network is connected to it.
Be prepared for the repair to have two stages — the wiring fault found and fixed, and then whatever was damaged while the voltage was present.
On this particular network there is one dominant cause, and it is worth raising immediately: anything fitted to the car after it was built.
This network runs to the doors, the boot and the centre console — exactly where a stereo, an amplifier, a subwoofer, a tracker, a dashcam or a light bar gets its power from. An installer looking for a live feed in a door or a boot panel is working centimetres from these wires.
So say what has been fitted, including anything a previous owner had done. Unplugging an accessory and re-testing is quicker than any measurement, and it settles a good proportion of these.
The car will probably still drive. Check your lights and indicators before driving at night.
What this code means
The positive line of the medium speed data bus is being held high. See U0005 for the warning that matters most — battery voltage on a bus wire can damage the transceiver in every module on the network, so the repair may have two stages.
One cause dominates on this bus specifically, and it is worth naming rather than leaving to the general list: audio and accessory installations.
This is the network that runs to the doors, the boot and the centre console — exactly where a stereo, an amplifier, a subwoofer, a tracker, a dashcam or a light bar gets its power feed run. An installer looking for a live in a door or a boot side panel is working centimetres from this pair.
Three specific ways it happens. A self-stripping connector clipped onto the wrong wire in a bundle. A power feed run through the same grommet and chafed against the pair. And a screw or self-tapper put through a loom while mounting an amplifier or a bracket.
So the first question is what has been fitted and by whom, including anything a previous owner had done — and unplugging an accessory to re-test is quicker than any measurement.
Expect the possibility that a module was damaged, and see U0005 before agreeing a fixed price for the repair.
Likely causes
Start here
- Poor wiring splice in an aftermarket installation · moderate
- Wiring shorted to voltage · moderate
- Faulty aftermarket alarm or immobiliser installation · moderate
- Damaged data bus wiring · moderate
Less common
- Damaged wiring harness · moderate
- Water ingress into connector · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
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